Current Electricity

Resistances are connected in a meter bridge circuit as shown in the figure. The balancing length \(l_{1}\) is \(40 \mathrm{~cm}\). Now an unknown resistance \(x\) is connected in series with \(\mathrm{P}\) and new balancing length is found to be \(80 \mathrm{~cm}\) measured from the same end. Then the value of \(x\) will be ____________ \(\Omega\).